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Results for “reliablity”

Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 919 records · Page 51
All sourcesNASA NTRSDOE OSTI
NASA NTRS1977

The influence of various test plans on mission reliability

Methods have been developed for the evaluation of cost effective vibroacoustic test plans for Shuttle Spacelab payloads. The shock and vibration environments of components have been statistically represented, and statistical decision theory has been used to evaluate the cost effectiveness of five basic test plans with structural test options for two of the plans. Component, subassembly, and payload testing have been performed for each plan along with calculations of optimum test levels and expected costs. The tests have been ranked according to both minimizing expected project costs and vibroacoustic reliability. It was found that optimum costs may vary up to $6 million with the lowest plan eliminating component testing and maintaining flight vibration reliability via subassembly tests at high acoustic levels.

Stahle, C. V.↗
NASA NTRS1977

Reliability measurement during software development

During the development of data base software for a multi-sensor tracking system, reliability was measured. The failure ratio and failure rate were found to be consistent measures. Trend lines were established from these measurements that provided good visualization of the progress on the job as a whole as well as on individual modules. Over one-half of the observed failures were due to factors associated with the individual run submission rather than with the code proper. Possible application of these findings for line management, project managers, functional management, and regulatory agencies is discussed. Steps for simplifying the measurement process and for use of these data in predicting operational software reliability are outlined.

Hecht, H.↗
NASA NTRS1978

Preliminary study of the reliability of imaging charge coupled devices

Imaging CCDs are capable of low light level response and high signal-to-noise ratios. In space applications they offer the user the ability to achieve extremely high resolution imaging with minimum circuitry in the photo sensor array. This work relates the CCD121H Fairchild device to the fundamentals of CCDs and the representative technologies. Several failure modes are described, construction is analyzed and test results are reported. In addition, the relationship of the device reliability to packaging principles is analyzed and test data presented. Finally, a test program is defined for more general reliability evaluation of CCDs.

Beall, J. R.↗
NASA NTRS1977

Reliability measurement during software development

Measurement of software reliability was carried out during the development of data base software for a multi-sensor tracking system. Every run made during this project was scored as success or failure, and supporting data were collected on forms for further analysis. The failure ratio (number of failures per calendar interval divided by total number of runs) and failure rate (number of failures divided by CPU time for the interval) were found to be consistent measures, on a month-to-month basis as well as from module to module, and therefore considered valid indicators of reliability in this environment. Trend lines could be established from these measurements that provide good visualization of the progress on the job as a whole as well as on individual modules. Over one-half of the observed failures were due to factors associated with the specific run submission rather than with the code proper.

Hecht, H.↗
NASA NTRS1979

Reliability of imaging CCD's

Report on reliability of imaging charge-coupled devices (CCD's) is intended to augment rather-meager existing information on CCD reliability. Study focuses on electrical and optical performance tests, packaging constraints, and failure modes of one commercially available device (Fairchild CCD121H).

Beal, J. R.↗
NASA NTRS1979

Redundant system reliability analysis

Computer Aided Redundant System Reliability Analysis (CARSARA) program facilitates reliability assessment of fault-tolerance reconfigurable systems. CARSRA accounts for influences from transient faults and is used to model wide range of redundancy management strategies.

Masreliez, C. J.↗
NASA NTRS1980

A reliable solid-state RF transfer switch

Highly-reliable lightweight solid-state RF (radio frequency) transfer switch replaces less reliable mechanical switch in handling medium power for S-band power amplifier.

Dodd, R. W.↗
NASA NTRS1978

On-orbit spacecraft reliability

Operational and historic data for 350 spacecraft from 52 U.S. space programs were analyzed for on-orbit reliability. Failure rates estimates are made for on-orbit operation of spacecraft subsystems, components, and piece parts, as well as estimates of failure probability for the same elements during launch. Confidence intervals for both parameters are also given. The results indicate that: (1) the success of spacecraft operation is only slightly affected by most reported incidents of anomalous behavior; (2) the occurrence of the majority of anomalous incidents could have been prevented piror to launch; (3) no detrimental effect of spacecraft dormancy is evident; (4) cycled components in general are not demonstrably less reliable than uncycled components; and (5) application of product assurance elements is conductive to spacecraft success.

Bloomquist, C.↗
NASA NTRS1978

The determination of measures of software reliability

Measurement of software reliability was carried out during the development of data base software for a multi-sensor tracking system. The failure ratio and failure rate were found to be consistent measures. Trend lines could be established from these measurements that provide good visualization of the progress on the job as a whole as well as on individual modules. Over one-half of the observed failures were due to factors associated with the individual run submission rather than with the code proper. Possible application of these findings for line management, project managers, functional management, and regulatory agencies is discussed. Steps for simplifying the measurement process and for use of these data in predicting operational software reliability are outlined.

Maxwell, F. D.↗
NASA NTRS1979

Trends in reliability modeling technology for fault tolerant systems

Reliability modeling for fault tolerant avionic computing systems was developed. The modeling of large systems involving issues of state size and complexity, fault coverage, and practical computation was discussed. A novel technique which provides the tool for studying the reliability of systems with nonconstant failure rates is presented. The fault latency which may provide a method of obtaining vital latent fault data is measured.

Bavuso, S. J.↗
NASA NTRS1980

Modified aerospace reliability and quality assurance method for wind turbines

The safety, reliability, and quality assurance (SR&QA) approach developed for the first large wind turbine generator project is described. The SR&QA approach was used to assure that the machine would not be hazardous to the public or operating personnel, would operate unattended on a utility grid, would demonstrate reliable operation and would help establish the quality assurance and maintainability requirements for future wind turbine projects. A modified failure modes and effects analysis during the design phase, minimal hardware inspections during parts fabrication, and three simple documents to control activities during machine construction and operation were presented.

Klein, W. E.↗
NASA NTRS1978

Study of turboprop systems reliability and maintenance costs

The overall reliability and maintenance costs (R&MC's) of past and current turboprop systems were examined. Maintenance cost drivers were found to be scheduled overhaul (40%), lack of modularity particularly in the propeller and reduction gearbox, and lack of inherent durability (reliability) of some parts. Comparisons were made between the 501-D13/54H60 turboprop system and the widely used JT8D turbofan. It was found that the total maintenance cost per flight hour of the turboprop was 75% higher than that of the JT8D turbofan. Part of this difference was due to propeller and gearbox costs being higher than those of the fan and reverser, but most of the difference was in the engine core where the older technology turboprop core maintenance costs were nearly 70 percent higher than for the turbofan. The estimated maintenance cost of both the advanced turboprop and advanced turbofan were less than the JT8D. The conclusion was that an advanced turboprop and an advanced turbofan, using similar cores, will have very competitive maintenance costs per flight hour.

Source record↗
NASA NTRS1980

Photovoltaic power system reliability considerations

An example of how modern engineering and safety techniques can be used to assure the reliable and safe operation of photovoltaic power systems is presented. This particular application is for a solar cell power system demonstration project designed to provide electric power requirements for remote villages. The techniques utilized involve a definition of the power system natural and operating environment, use of design criteria and analysis techniques, an awareness of potential problems via the inherent reliability and FMEA methods, and use of fail-safe and planned spare parts engineering philosophy.

Lalli, V. R.↗
NASA NTRS1979

Reliability measurement for operational avionics software

Quantitative measures of reliability for operational software in embedded avionics computer systems are presented. Analysis is carried out on data collected during flight testing and from both static and dynamic simulation testing. Failure rate is found to be a useful statistic for estimating software quality and recognizing reliability trends during the operational phase of software development.

Thacker, J.↗
NASA NTRS1980

Photovoltaic power system reliability considerations

This paper describes an example of how modern engineering and safety techniques can be used to assure the reliable and safe operation of photovoltaic power systems. This particular application was for a solar cell power system demonstration project in Tangaye, Upper Volta, Africa. The techniques involve a definition of the power system natural and operating environment, use of design criteria and analysis techniques, an awareness of potential problems via the inherent reliability and FMEA methods, and use of a fail-safe and planned spare parts engineering philosophy.

Lalli, V. R.↗
NASA NTRS1982

Reliable "Unlatch"

Reliable unlatching mechanism utilizes preloading, a favorable geometric arrangement of mating surfaces, and redundancy to assure release. Even if only one rocking arm initially releases, the entire assembly will rotate or rock sideways to complete unlatching. Device could be useful in other applications requiring reliable remote disconnection of cables or pipes.

Killgrove, T. O.↗
NASA NTRS1981

Approach to reliability when applying new technologies

Tactical weapon systems, while different in many respects from PTTI applications, face similar risks in achieving reliability in development. General principles derived from experience in achieving high reliability in tactical weapon systems are selectively summarized for application to new technologies in unusual environments.

Bear, J. C.↗